Fuel cell stack and fuel cell system equipped with fuel cell stack

Abstract

The present invention relates to a fuel cell stack (3) comprising a plurality of individual cells (24), wherein the individual cells (24) have a common cathode region (5) and a common anode region (4) separated from the common cathode region (5). The fuel cell stack according to the present invention is characterized by having at least one valve device (20, 21) integrated to block a flow path into and / or out of the cathode region (5).

Description

Technology Field

[0001] The present invention relates to a fuel cell stack comprising a plurality of individual cells having a common cathode region and a common anode region, and a fuel cell system having the fuel cell stack. In particular, the present invention relates to a fuel cell stack comprising a plurality of individual cells having a common cathode region and a common anode region separated from the common cathode region, and a fuel cell system having the fuel cell stack. Background Technology

[0002] Fuel cell stacks composed of multiple individual cells are generally disclosed in the prior art. Generally, individual cells are fixed between two end plates, and a common cathode region and a common anode region are formed for all individual cells of the fuel cell stack. The inlet and outlet regions for this purpose generally extend along the entire length of the stack in the stack direction and are formed by an opening formed in the individual cells, said openings connecting all cells of the fuel cell stack in parallel with each other in relation to the perfusion of gas extract.

[0003] In practice, this type of fuel cell stack is now being used in fuel cell systems. When a fuel cell stack is designed with individual cells of PEM technology—that is, proton-conducting membranes or polymer electrolyte membranes—gas within the fuel cell system is flushed through the fuel cell stack when new gas is metered and added for startup. This is particularly important in the anode region. After the fuel cell stack has finished operating, if the hydrogen in the anode region has evaporated or been consumed by the subsequent flowing oxygen in the fuel cell, air is primarily present in the anode region. Now, when hydrogen is metered and added, the air / hydrogen wires flow in parallel through all individual cells of the fuel cell stack. This causes a critical potential difference in the wires along with the air in the cathode region, which damages the fuel cell's catalytic converter. This startup, also known as air / air startup of the fuel cell stack, has an undesirable effect on its lifespan.

[0004] To prevent this, for example, hydrogen that is not consumed during the entire shutdown time of the fuel cell stack can ideally be stored in the anode region. One mechanism for this is to prevent subsequent air flow into the cathode region. In fuel cell systems disclosed in the prior art, valve devices are primarily used to shut off the cathode region of the fuel cell stack during the shutdown state of the fuel cell system. These components, also known as cathode shut-off valves, are often large valves or flaps used at the periphery of the fuel cell stack. These components are heavy, prone to failure and leakage, and are relatively expensive, at least in the case of a sufficiently sealed structure. Furthermore, these components require a relatively large assembly space along with control electronics and actuators to control the valve. The problem to be solved

[0005] The objective of the present invention is to further improve a fuel cell stack according to the type mentioned in the preamble of claim 1 to enable a long lifespan, and to provide an improved fuel cell system equipped with such a fuel cell stack. means of solving the problem

[0006] According to the present invention, these problems are solved by a fuel cell stack having the features of claim 1, in particular the features of claim 1, and a fuel cell system having the features of claim 15. Preferred embodiments and further improvements are set forth in dependent claims dependent thereon.

[0007] A fuel cell stack according to the present invention is provided with at least one valve device integrated to block a flow path to and / or from the cathode region, particularly into and / or out of the cathode region, particularly a flow path of a cathode gas including air. This integration of the valve device inside the fuel cell stack enables the saving of such valve device within the fuel cell system area, particularly outside the fuel cell stack, and thus contributes decisively to saving assembly space, particularly for the fuel cell system. In this case, the single valve device appropriately blocks the flow path passing through the cathode region in advance, so that flow through the cathode region is no longer possible. This already ensures a very positive effect, as air in the cathode region can be exchanged only through a convection process at one side of the valve, specifically at the other side of the valve device.

[0008] According to a highly preferred improved embodiment of the fuel cell stack according to the present invention, at least one valve device is designed to be integrated into at least one end plate. As described above, individual cells of the fuel cell stack are fixed together mainly between two end plates. In the area of ​​these end plates having a thickness greater than that of each individual cell of the fuel cell stack, there is generally sufficient assembly space to integrate the valve device in the manner described above. For example, the valve device, in particular, can be integrated into the inlet air connection and / or the exhaust air connection by screwing it into the end plate from the connection side of the inlet air line and / or the exhaust air line to the fuel cell stack.

[0009] At least one valve unit may also be designed as a normally closed valve unit. Such a normally closed valve unit ensures the sealing of the flow path passing through the cathode region of the fuel cell stack without active operation and without permanent energy requirements. Since active operation for opening can be performed, for example, by electromagnetic force, the valve unit must be switched as intended in this way.

[0010] As an alternative to this, it may be considered that a structure requiring no control can be formed by using a permanent magnet in combination with a magnetizable valve body and / or valve seat to provide spring pressure and / or magnetic force, particularly a magnetic force opposing the permanent magnetic force.

[0011] In particular, magnetic force provides a decisive advantage because it can or can form a passive, magnetically damping valve device. Magnetic damping means that the valve device is normally kept closed by a magnet, and in this case, the force maintaining the valve device in the closed state is large. Unlike a valve subjected to a spring load, where the closing force increases as it opens, the force to close the valve again after opening decreases as it gradually opens.

[0012] In particular, the valve body is retained at the valve seat when there is no inflow to the valve seat, especially at an appropriate pressure and / or flow rate. In this non-operating state, the structure is sealed and may have one or more sealing parts or sealing members, which are preferably positioned in the slipstream of the valve body and, on the one hand, ensure a good seal and do not cause unnecessary pressure loss during flow.

[0013] When using a passive, magnetically damped valve device, the valve body of the valve device is held in the valve seat in a particularly stable and sealed manner by one or more (permanent) magnets together with one or more other (permanent) magnets and / or the magnetizable area of ​​the valve body and / or the magnetizable area of ​​the valve seat; thus, the blocking function caused by the valve device to block the flow path is particularly pronounced. As a result, the number of harmful air / air starts that promote performance degradation of the fuel cell stack is reduced, and the hydrogen protection time can be extended.

[0014] When air or cathode gas supplied through an intake air line and one or more air supply devices, such as flow compressors, is actively introduced into the cathode region, the pressure and flow velocity of the supplied air ensure that the valve body is lifted from the valve seat against spring force and / or, particularly preferably, against magnetic force, and that upon activation of the air supply, the valve device automatically initiates flow into the cathode region. In particular, the magnetic force of a permanent magnet, which may be positioned within or spaced apart from the valve seat, can ensure stable flow of the valve device at various flow volumes in conjunction with a magnetizable valve body. The overall structure is lightweight and robust, and due to the use of magnets and the typical damping force-displacement behavior of these magnets, unimpeded flow is enabled at both minimum and maximum flow volumes sufficient to open the valve device. In the case of such flow, due to the progressive force-displacement characteristic curve of an ideal magnet, flow occurs without permanent change between the opening and closing of the valve or valve device in both cases, so pressure pulsation in the cathode region can be reliably prevented, and the valve(s) or valve device(s) can operate efficiently and with low noise. This is also called "chatter-free" operation.

[0015] In addition, the required assembly space can be further reduced by using at least one passive, self-damping valve unit, as additional assembly space for cabling and / or control units is not required.

[0016] The valve body itself can preferably be designed as a soft magnetic component, particularly a soft magnetic rotating component, or may include a soft magnetic, particularly magnetizable material and / or a permanent magnet, and preferably may be designed in a shape optimized for flow.

[0017] According to a highly preferred improved embodiment of the fuel cell stack according to the present invention, the valve body has an end facing the inlet of at least one valve device, said end having a groove or trough, in the embodiment an annular groove or trough, and in the embodiment the end of the valve body faces upward when used as intended.

[0018] As a result, in the embodiment, liquid such as water escaping from the cathode region can be collected by a groove or trough.

[0019] According to a highly preferred improved embodiment of a fuel cell stack according to the present invention, at least one valve device comprises a guide device having one or more guide surfaces, said guide surfaces are configured to guide the opening and closing movement of a valve body, said guide device has a cylindrical section, and the valve body has at least one protrusion extending in the direction of the discharge portion of at least one valve device, wherein in the embodiment, the central protrusion of the at least one protrusion extends into a cavity formed by the cylindrical section of the guide device and / or the protrusion of the at least one protrusion surrounds the end of the cylindrical section of the guide device facing the inlet portion of at least one valve device.

[0020] Consequently, in the embodiments, the movement of the valve body can be reliably prevented from being restricted and / or blocked, for example by tilting.

[0021] According to a highly preferred improved embodiment of the fuel cell stack according to the present invention, the end of a cylindrical section of a guide device separated from the inlet of at least one valve device is closed or has a passage.

[0022] Consequently, in an embodiment where the cylindrical section of the guide device has a passage, any liquid, such as water, can flow out of the valve device through the valve discharge after passing through the passage.

[0023] According to a highly preferred improved embodiment of the fuel cell stack according to the present invention, at least one valve device has a magnet mounted on a guide device in the embodiment, which is fixed, and a magnet mounted on a valve body, which is movable together with the valve body, and in this case, the fixed magnet and the magnet movable together with the valve body are attracted to each other by the magnetic force between the fixed magnet and the magnet movable together with the valve body.

[0024] Consequently, in the embodiments, it is preferable that the closing force be further reduced as the cathode shut-off valve gradually opens.

[0025] During subsequent operation, a hydrophobic surface may be provided in an area where the valve body contacts the valve seat or where only a small flow cross-section between the valve body and the surrounding material is open. Such a hydrophobic surface can be realized, for example, by appropriate surface treatment or coating. To prevent water accumulation in areas critical to the operation of the valve device, while simultaneously forming an area where water accumulation can occur without being a problem, such a hydrophobic surface is preferably provided in the valve device in conjunction with a hydrophilic surface. This allows unavoidable water accumulation in the cathode region of the fuel cell stack, particularly in the region of the effluent medium, to be directed to a location where it is not a problem, even if the water freezes there in some cases.

[0026] In this case, at least one valve device may have a region having a particularly hydrophobic surface, and in the embodiment, the surface of the valve seat and / or the sealing member disposed in the region of the valve seat and / or the surface of the valve body are designed to be hydrophobic, the surface of the valve seat and / or the sealing member faces the surface of the valve body, and / or the guide face of the guide device and / or the end face of the guide device facing the inlet of the valve device and / or the surface section of the valve body facing the guide device are designed to be hydrophobic.

[0027] Consequently, in the examples, the accumulation of liquid, particularly water, in areas with hydrophobic surfaces can preferably be prevented at least mostly.

[0028] Additionally, in this case, at least one valve device may include a region having a particularly hydrophilic surface, and in the embodiment, the surface of the groove and / or the surface of the undercut provided on the side of the valve body in the section of the fuel cell stack in which the valve device is integrated, facing the direction of the discharge portion of the valve device, is designed to be hydrophilic.

[0029] Consequently, in the embodiments, it is achieved that a liquid, such as water, which is sometimes contained in the cathode gas, accumulates in these areas with hydrophilic surfaces and can be removed at least occasionally from the fuel cell stack or the rest of the system. Even if ice forms in these areas due to low temperatures caused by this accumulation of water, this has little to no effect on the operation of the valve device, because the mobility of the valve body is not restricted, particularly as can occur due to freezing of the valve body at the valve seat or sealing member.

[0030] According to a highly preferred improved embodiment of the fuel cell stack according to the present invention, valve devices may be provided to be formed on the inlet side and the outlet side of the cathode region, respectively. In this particularly preferred improved embodiment of the fuel cell stack according to the present invention, the fuel cell stack has two separate valve devices capable of blocking the fuel cell stack on the inlet side and the outlet side when not in operation to safely and reliably prevent subsequent air flow due to convection effects, wall effects, etc.

[0031] According to another highly preferred embodiment of the fuel cell stack according to the present invention, additionally, two valve devices may be designed as identical parts. The two valve devices can therefore be designed as identical parts, which makes the overall structure cheaper because each valve device is manufactured with a larger number of parts, thereby causing a scaling effect. In this case, the valve devices are installed within the fuel cell stack with opposite fitting positions so that they flow in the same direction on the inlet and outlet sides.

[0032] A fuel cell system according to the present invention comprises the aforementioned fuel cell stack, wherein the fuel cell stack has a valve device integrated into the fuel cell stack and disposed downstream of the discharge portion of the cathode region, wherein the valve device is designed as a passive, self-damping valve device in the embodiment, and the fuel cell system further comprises a (active) multi-way valve disposed upstream of the inlet portion of the cathode region and a gas jet pump having at least one suction inlet and a driving inlet, wherein the inlet portion of the multi-way valve is connected to an inlet air line of the cathode region, the first discharge portion of the multi-way valve is connected to the inlet portion of the cathode region, the second discharge portion of the multi-way valve is connected to the driving inlet portion of the gas jet pump, wherein the suction inlet portion of at least one suction inlet portion of the gas jet pump is switchedably connected to the discharge portion of the cathode region upstream of the valve device in the embodiment by a cathode suction valve in the embodiment and / or the other suction inlet portion of at least one suction inlet portion of the gas jet pump is switchedably connected to the discharge portion of the anode region in the embodiment by a purge- / drain valve in the embodiment through a recirculation line connected to the discharge portion of the anode region in the embodiment.

[0033] Consequently, liquids such as water and gases such as air, which are present in some cases due to or after evaporation at low pressure, can be drawn from the volume of the cathode region as well as the anode region, even at low temperatures. Ideally, the drawing is carried out relatively uniformly to prevent an excessively high pressure difference between the cathode and anode regions and thereby protect the membrane.

[0034] In this case, the disadvantage of requiring cabling to control an active multi-way valve can be accepted for the advantage that low pressure can be applied to the fuel cell stack, which would be impossible with two passive valve devices on the input- and output sides of the cathode region because one of them would always be open.

[0035] According to another highly preferred embodiment of the fuel cell system according to the present invention, the second discharge portion of the multi-directional valve is connected to the discharge air line of the cathode region through a cathode bypass line in which a gas jet pump is disposed.

[0036] According to another highly preferred embodiment of the fuel cell system according to the present invention, a multi-directional valve is integrated into a component of the fuel cell system.

[0037] As a result, the assembly space required for the fuel cell system in the examples can be reduced.

[0038] According to another highly preferred embodiment of the fuel cell system according to the present invention, the system may further include, as components, a gas / gas humidifier disposed upstream of the inlet of the cathode region and a gas / gas humidifier bypass line connected to an inlet air line upstream of the gas / gas humidifier and connected to an outlet air line upstream of the cathode region, and the multi-way valve is integrated with the gas / gas humidifier, in the embodiment, together with the humidifier bypass flap of the gas / gas humidifier and / or a gas jet pump is disposed in the gas / gas humidifier bypass line in such a way that a second outlet of the multi-way valve is connected to the drive inlet of the gas jet pump.

[0039] Another preferred embodiment of the fuel cell stack according to the present invention is presented in an embodiment described in more detail below with reference to the drawings. Brief explanation of the drawing

[0040] FIG. 1 is a drawing illustrating a fuel cell system of design according to the prior art. FIG. 2 is a drawing illustrating a fuel cell stack of a possible embodiment according to the present invention. FIG. 3 is a drawing illustrating a valve device for a fuel cell stack of a possible embodiment according to the present invention. FIG. 4 is a plan view showing a part of the valve device illustrated in FIG. 3 in the flow direction. FIG. 5 is a diagram illustrating the functional relationship of the closing force of a valve device with respect to the degree of opening of the valve device. FIG. 6 is a schematic diagram illustrating a part of a fuel cell system of a possible embodiment according to the present invention. Specific details for implementing the invention

[0041] FIG. 1 illustrates, for example, a fuel cell system (1) that can be provided to a vehicle (2) to provide electric driving power, shown in great schematic detail. A fuel cell stack (3) forms the core of this fuel cell system (1), and the fuel cell stack is often referred to as a fuel cell or a fuel cell stack. It is generally composed of a number of stacked individual cells (24) (see FIG. 2). A common anode chamber (4) or anode region (4) and a common cathode chamber (5) or cathode region (5), separated by a proton-conducting membrane (6), are shown here purely by example. Thus, the fuel cell stack (3) is a PEM fuel cell stack.

[0042] Hydrogen is supplied to the anode chamber (4) from a hydrogen source (7), for example, a pressurized gas storage unit or a cryogenic storage unit. This hydrogen reaches the anode chamber (4) of each individual cell through a pressure regulating and metering unit (8). Unconsumed hydrogen can be recirculated through a recirculation transfer unit (10), where, for example, a recirculation line (9) with a recirculation fan. Occasionally, water and hydrogen can be discharged from a water separator (11) and released through a purge and drain valve (12).

[0043] Air is supplied to the cathode region (5) of the fuel cell system (1) as an oxygen supplier through the inlet air line (13). The exhaust air is discharged out of the fuel cell system (1) through the exhaust air line (14). A flow compressor (15) is placed here to transport the necessary air. After the flow compressor (15), the hot and dry air reaches the cathode region (5) through a gas / gas humidifier (16) and, in some cases, a supercharged air cooler not shown here. The humid exhaust air from the cathode region (5) passes through the exhaust air line (14) and again through the gas / gas humidifier (16), and in the region of the humidifier, the exhaust air releases moisture into the dry and hot inlet air and then flows around through the exhaust air turbine (19) in the embodiment shown here. The exhaust air turbine (19) and the flow compressor (15) are connected to each other via a common shaft (17) and an electric machine (18), so that the energy generated in the area of ​​the exhaust air turbine (19) can be used to support the driving of the air transport device (15) and for the regenerative driving of the electric machine (18) when driving power is not required.

[0044] A fuel cell system (1) according to the prior art now has two cathode shut-off valves (20, 21) in the intake air line (13) as in the exhaust air line (14), here purely exemplarily between the gas / gas humidifier and the fuel cell stack (3). These cathode shut-off valves (20, 21) are generally designed as active-controlled flaps, and said flaps require a relatively large assembly space within the fuel cell system (1), and thus are costly and complex in terms of assembly and control.

[0045] Nevertheless, the effect of these cathode shut-off valves (20, 21) on the lifespan of the fuel cell stack (3) is positive, because the shut-off valves can prevent subsequent flow of fresh air into the cathode region (5), which ultimately, in the ideal case, only nitrogen is present there after a longer period of standby of the fuel cell system (1), and hydrogen in the node region (4) is no longer consumed through the fuel cell stack (3) during standby. Thus, when restarting the fuel cell system (1) or the fuel cell stack (3), dangerous air / air start-up to the lifespan of the fuel cell stack (3) can be prevented.

[0046] Now, a schematic diagram of a fuel cell stack (3) of a possible modified embodiment according to the present invention is shown in FIG. 2. In this case, a plurality of individual cells (24) are fixed between two end plates (22, 23), some of which are given reference numerals, and each of the individual cells has a cathode region (5) or cathode chamber (5), an anode region (4) or anode chamber (4), and a membrane (6). The individual anode region (4) and cathode region (5), as well as the cooling medium flow region forming a cooling heat exchanger within the fuel cell stack (3), are connected to each other through the through-holes of the individual cells (24). In the region of the first end plate (22), hydrogen is supplied to the anode region (4) through a hydrogen supply line (25), and in the region of the other end plate (23), it is discharged to a recirculation line (9). In addition, FIG. 2 shows a cooling medium supply section (26) in the area of ​​the first end plate (22) and a cooling medium discharge section (27) in the area of ​​the other end plate (23).

[0047] The inlet air line (13) is connected to the first end plate (22), and the exhaust air line (14) is connected to the second end plate (23). Instead of cathode shut-off valves (20, 21) in the area of ​​the fuel cell system (1), these valves are now integrated into the fuel cell stack (3), and preferably integrated into each end plate (22, 23) as schematically illustrated herein. Thus, the end plate (22) supports the inlet air side cathode shut-off valve (20), which is a valve device integrated in itself in relation to the present application, and the other end plate (23) likewise supports the exhaust air side cathode shut-off valve (21), which is a valve device in relation to the present application. Ideally, the cathode shut-off valve (22, 21) integrated into each end plate (22, 23) of the fuel cell stack (3) is designed to be passive, that is, normally closed and then opened accordingly by flowing incoming air or flowing outgoing air, so that it can be implemented simply and efficiently within the fuel cell system (1) and with minimal assembly space requirements.

[0048] Now, FIG. 3 shows a schematic diagram of a cathode shut-off valve (20, 21) integrated into a section of the fuel cell stack (3) shown in FIG. 2, according to a possible modified embodiment of the present invention.

[0049] A cathode shut-off valve (20, 21) or valve device (20, 21) has a valve body (101) disposed in a cavity of a section of a fuel cell stack (3). The valve body (101) is disposed movably, particularly linearly movably, within a cavity of a section of the fuel cell stack (3) along the direction of flow of (cathode) gas or (cathode) fluid flowing into or out of the cathode region (5) that exists when used as intended, at least partially illustrated by the arrow (P1) in FIG. 3, and opposite to the direction of flow of the cathode gas. In this case, the cross-section of the cavity of the section of the fuel cell stack (3) or the region of the fuel cell stack (3) surrounding the cavity is tapered in the opposite direction to the direction of flow of the cathode gas, so that the movement of the valve body (101) in the opposite direction to the direction of flow of the cathode gas is limited by the tapered cross-section. The valve seat (120) of the cathode shut-off valve (20, 21) is formed by a section of the fuel cell stack (3) in which the cross section is tapered.

[0050] When the valve body (101) contacts the valve seat (120), the cathode shut-off valve (20, 21) is in a closed position when the valve body (101) contacts the sealing member (102), which is disposed in the area of ​​the valve seat (120) in the embodiment and is formed as an O-ring, for example as shown in FIG. 3, while the cathode shut-off valve (20, 21) is in an open position when the valve body (101) is not in contact with the valve seat (120) or when the valve body (101) is not in contact with the sealing member (102).

[0051] To guide the movement of the valve body (101) within the fuel cell stack (3), particularly the opening and closing movement, the cathode shut-off valve (20, 21) further has a guide device (112) having one or more guide surfaces, said guide surfaces are set to cause the movement of the valve body (101) by sliding along said guide surfaces, especially when the valve body (101) moves.

[0052] The guide device (112) is mounted on the inner side of a section of the fuel cell stack (1) surrounding the cavity by one or more, preferably three, fixing members (106), particularly fin-type fixing members (106), thereby determining the position of the guide device (112) within the fuel cell stack (1). FIG. 4 shows a plan view corresponding to the flow direction of the cathode gas of the guide device (112) including the fixing members (106).

[0053] The guide device (112) preferably has a cylindrical section extending parallel to the flow direction of the cathode gas, and in the embodiment, the end of the cylindrical section away from the inlet of the cathode shut-off valve (20, 21) can be closed, and in another embodiment shown in FIG. 3, it can have a passage (105) through which any liquid present, such as water, can be discharged.

[0054] The valve body (101) has one or more protrusions extending in the direction of the discharge portion of the cathode shut-off valve (20, 21), in which case one of the protrusions, particularly the central protrusion, extends into the cavity formed by the cylindrical section of the guide device (112), and the other of the protrusions surrounds the end of the cylindrical section of the guide device (112) facing the inlet portion of the cathode shut-off valve (20, 21).

[0055] The cathode shut-off valve (20, 21) is designed as a self-damping valve, and the valve is normally maintained in a closed position by magnetic force, particularly when the pressure difference between the pressure on the inlet side of the cathode shut-off valve (20, 21) and the pressure on the outlet side of the cathode shut-off valve (20, 21) is smaller than a predetermined threshold value. The force maintaining the cathode shut-off valve (20, 21) in the closed position is relatively large, and in this case, as illustrated in the diagram of FIG. 5, the closing force (F) for moving the cathode shut-off valve (20, 21) back to the closed position after opening the cathode shut-off valve (20, 21) decreases as it is gradually opened or as the distance from the valve seat (120) or sealing member (102) to the valve body (101) increases.

[0056] To this end, the cathode shut-off valve (20, 21) has one or more magnets (104) formed as permanent magnets having a north and south pole (104-1, 104-2) disposed within the area of ​​the valve seat (120) or spaced apart from the valve seat (120), in which case the valve body (101) has a magnetizable material and / or a (permanent-) magnet having the same polarity as the magnet (104) in at least partially, particularly in one or more area(s) facing the magnet(s) (104) and / or in one or more area(s) (116) in close proximity to the magnet(s) (104), particularly the closest one. Consequently, the valve body (101) is driven in the direction of the inlet of the cathode shut-off valve (20, 21) by the magnetic force generated between the magnet (104) and the magnetizable material and / or (permanent-) magnet of the valve body (101).

[0057] In an optional embodiment, a fixed (permanent-) magnet (108) having a north pole and a south pole (108-1, 108-2), preferably mounted on a guide device (112), is additionally provided inside a cylindrical section of the guide device (112), and a (permanent-) magnet (107) having a north pole and a south pole (107-1, 107-2) that is mounted on a valve body (101) and movable together with it, and has a polarity that matches the polarity of the magnet (104), is provided so that the attractive force and closing force between the two magnets (107, 108) are further reduced as the cathode shut-off valve (20, 21) gradually opens.

[0058] The valve body (101) has a groove or trough (110), particularly an annular groove or trough (110), capable of collecting liquid such as water flowing out of the cathode region (5) when the cathode shut-off valve (20, 21) is integrated at the end facing the inlet of the cathode shut-off valve (20, 21), particularly on the outlet side of the cathode region (5). To this end, the cathode shut-off valve (20, 21) or the valve body (101) is preferably mounted within the fuel cell stack (3) such that, when used as intended, the exposed surface of the trough (110) faces upward, so that liquid within the trough (110) falling from above and colliding with the valve body (101) can be collected by the trough (110).

[0059] In an embodiment, the surface of the trough (110) is designed to be hydrophilic, as shown by the dashed line with reference numeral 103 in FIG. 3. In an embodiment, the surface of the undercut (113) provided on the side of the valve body (101) in the section of the fuel cell stack (3) incorporating the valve device (20, 21), facing the direction of the discharge portion of the cathode shut-off valve (20, 21), is also designed to be hydrophilic, as shown by the dashed line (114).

[0060] Due to the hydrophilic design of the surface of the trough (110) and / or the surface of the undercut (113), liquids such as water, which are in some cases like those contained in the cathode gas, accumulate at these points and are therefore removed at least occasionally from the rest of the fuel cell stack (3) or fuel cell system (1). Even if ice forms at these points due to low temperatures caused by this accumulation of water, this has little to no effect on the operation of the cathode shut-off valve (20, 21) because it does not restrict the mobility of the valve body (101), particularly as can be caused by freezing of the valve body at the valve seat (120) or sealing member (102).

[0061] In order to prevent freezing of the valve body (101) at the valve seat (120) or sealing member (102) as much as possible, the surface of the valve seat (120) and / or sealing member (102) and / or the surface of the valve body (101) and / or guide face(s) and / or the guide device (112) and / or the end face of the section of the valve body (101) facing the guide device (112) facing the inlet of the cathode shut-off valve (20, 21) are also designed to be hydrophobic as shown by the dashed line with reference numeral 109, so that the accumulation of liquid, particularly water, at this point can be prevented at least mostly.

[0062] The hydrophobicity / hydrophilicity of the above region or surface can be achieved, for example, by a) selecting a corresponding hydrophobic / hydrophilic material; b) polishing each surface for hydrophobicity or roughening each surface for hydrophilicity; c) plasma treating each surface; or d) causing capillary forces by forming lamellae on each surface, for example.

[0063] Now, FIG. 6 shows a schematic diagram of a part of a fuel cell system of a possible embodiment according to the present invention.

[0064] In this embodiment, the fuel cell system (1) has only one cathode shut-off valve (20, 21) integrated into the fuel cell stack (3), particularly, for example, the passive, self-damping cathode shut-off valve (21) shown in FIG. 3, said valve is positioned near the discharge portion of the cathode region (5).

[0065] In contrast, preferably on the inlet side of the cathode region (5) which is placed in the inlet air line (13) or integrated into another component of the fuel cell system (1), a multi-way valve (204), particularly a 3 / 2 direction valve, which operates as an active or actively controllable cathode shut-off valve is placed.

[0066] In an embodiment not illustrated, the multi-directional valve (204) is integrated into a humidifier unit such as an air treatment unit (LAE) or a gas-gas humidifier (16), and is also integrated therein with a humidifier bypass flap or control function or generally provided with a humidifier bypass flap or control function.

[0067] The inlet of the multi-way valve (204) is connected to the inlet air line (13). The first outlet of the multi-way valve (204) is connected to the inlet of the cathode region (5), and the flow path to the cathode region is blocked by blocking the first outlet of the multi-way valve (204). The second outlet of the multi-way valve (204) is connected to the exhaust air line (14) of the cathode region (5) downstream of the cathode shut-off valve (21) through a cathode bypass line (208) to which a catalytic converter (206) may be optionally provided, as shown in FIG. 6.

[0068] The cathode shut-off valve (21) and the multi-way valve (204) integrated into the fuel cell stack (3) are connected to each other, particularly through a gas jet pump or a suction jet pump or a jet pump (203), which may include, for example, a venturi nozzle or is formed as a venturi nozzle and is driven by cathode gas flowing through a cathode bypass line (208) as a driving jet flowing into the driving inlet of the gas jet pump (203). In this case, a blow-off line (209) connected to the recirculation line (9), particularly connected to the discharge of a water separator (205) placed in the recirculation line (9), is connected to the suction inlet of the gas jet pump (203) through a blow-off valve or a purge valve (202) or a purge- / drain valve (202). Additionally, the cathode branch line (207) connected to the discharge portion of the cathode area (5) upstream of the cathode shut-off valve (21) is connected to another suction inlet of the gas jet pump (203) through the cathode suction valve (201).

[0069] In this way, low pressure can be applied to the cathode region (5) on one side by switching the cathode suction valve (201) to the second discharge section to connect the incoming air line (13) to the outgoing air line (14) through the gas jet pump (203), and low pressure can be applied to the anode region (4) on the other side by switching the purge- / drain valve (202) to the second discharge section to connect the incoming air line (13) to the outgoing air line (14) through the gas jet pump (203).

[0070] Thus, liquids and gases such as air, which are present in cases such as water due to or after evaporation at low pressure, can be drawn in from the volume of the anode region (4) or the anode circuit, as well as from the volume of the cathode region (5), even at low temperatures. Ideally, the suction is relatively uniform to protect the membrane by preventing an excessively high pressure difference between the cathode region (5) and the anode region (4). In a fuel cell system (1) having two manual cathode shut-off valves (20, 21) on the inlet- or outlet side of the cathode region (5), these (suction- and evaporation) functions cannot be used because one of the cathode shut-off valves (20, 21), particularly the cathode shut-off valve (20) on the inlet side, is always open due to suction.

[0071] In an embodiment not illustrated, the gas jet pump (203) may be integrated into the bypass of an air treatment unit (LAE) or a humidifier unit, such as a gas humidifier (16), preferably with a multi-way valve (204) as an alternative, and may also be integrated therein with a humidifier bypass flap or control function generally provided therein. In this case, the gas jet pump (203) may be driven by gas as a driving jet flowing through the bypass, and the gas jet pump (203) may be switchably connected to the cathode area (5) or anode area (4) on the suction side through a cathode suction valve (201) or a purge- / drain valve (202) and a corresponding line so that they can be sucked in and emptied.

Claims

Claim 1 A fuel cell stack (3) comprising a plurality of individual cells (24), wherein the individual cells (24) have a common cathode region (5) and a common anode region (4) separated from the common cathode region (5), and at least one valve device (20, 21) is integrated to block a flow path into the cathode region (5), out of the cathode region (5), or both, wherein the at least one valve device (20, 21) is designed as a normally closed valve device (20, 21), and the valve body (101) of the at least one valve device (20, 21) is kept open against spring pressure, or against magnetic force, or both when there is sufficient volumetric flow through the cathode region (5), and the valve body (101) is formed of a soft magnetic material or comprises a soft magnetic material, or a permanent magnet, or both, and at least one permanent magnet (104) is formed in the valve seat region. A fuel cell stack configured to be magnetically operated directly or indirectly connected to a seat (120), wherein at least one valve device (20, 21) has a fixed magnet (108) and a magnet (107) mounted on the valve body (101) and movable together with the valve body (101), and wherein the fixed magnet (108) and the magnet (107) movable together with the valve body (101) are attracted to each other by the magnetic force between the fixed magnet (108) and the magnet (107) movable together with the valve body (101). Claim 2 A fuel cell stack according to claim 1, wherein the at least one valve device (20, 21) is integrated into at least one end plate (22, 23). Claim 3 A fuel cell stack according to claim 1, wherein the valve body (101) has an end facing the inlet of the at least one valve device (20, 21) having a groove (110), and the end of the valve body (101) faces upward when used as intended. Claim 4 A fuel cell stack according to claim 3, wherein the at least one valve device (20, 21) comprises a guide device (112) having one or more guide surfaces, the guide surfaces are configured to guide the opening and closing movement of the valve body (101), the guide device (112) has a cylindrical section, and the valve body (101) has at least one protrusion extending in the direction of the discharge portion of the at least one valve device (20, 21), wherein the central protrusion of the at least one protrusion extends into a cavity formed by the cylindrical section of the guide device (112) or the protrusion of the at least one protrusion surrounds the end of the cylindrical section of the guide device (112) facing the inlet portion of the at least one valve device (20, 21). Claim 5 A fuel cell stack according to claim 4, characterized in that the end of the cylindrical section of the guide device (112) separated from the inlet of at least one valve device (20, 21) is closed or has a passage (105). Claim 6 In claim 4, the at least one valve device (20, 21) has a region (103, 111) having a hydrophobic surface, and at least one of the surface of the valve seat (120), or the surface of the sealing member (102) disposed in the region of the valve seat (120), and the surface of the valve body (101) is hydrophobic, and the surface of the valve seat (120), or the surface of the sealing member (102) faces the surface of the valve body (101), or at least one of the guide surface of the guide device (112), the end surface of the guide device (112) facing the inlet of the valve device (20, 21), and the surface section of the valve body (101) facing the guide device (112) is hydrophobic, characterized in that the fuel cell stack is characterized in that Claim 7 In claim 4, the fuel cell stack is characterized in that at least one valve device (20, 21) comprises a region (103) having a hydrophilic surface, and at least one of the surfaces of the groove (110) and the undercut (113) provided on the side of the valve body (101) in the section of the fuel cell stack (3) in which the valve device (20, 21) is integrated, facing the direction of the discharge portion of the valve device (20, 21), is hydrophilic. Claim 8 A fuel cell stack according to claim 1 or 2, characterized in that a sealing member (102) placed in the wake of the flow is positioned in the area of ​​the valve seat. Claim 9 A fuel cell stack according to claim 1 or 2, characterized in that at least one valve device (20, 21) is formed on the inlet side and the outlet side of the cathode region (5), respectively. Claim 10 A fuel cell stack according to claim 9, characterized in that the two valve devices (20, 21) are designed as identical parts. Claim 11 A fuel cell system (1) having a fuel cell stack (3) according to claim 1 or 2, wherein the fuel cell stack (3) has a valve device (21) integrated into the fuel cell stack (3) and disposed downstream of the discharge portion of the cathode region (5), and the valve device (21) is designed as a passive, self-damping valve device (21), and the fuel cell system (1) has a multi-directional valve (204) disposed upstream of the inlet portion of the cathode region (5); A fuel cell system further comprising a gas jet pump (203) having at least one suction inlet and a drive inlet, wherein the inlet of the multi-directional valve (204) is connected to an inlet air line (13) of the cathode region (5), the first outlet of the multi-directional valve (204) is connected to an inlet of the cathode region (5), and the second outlet of the multi-directional valve (204) is connected to a drive inlet of the gas jet pump (203), and wherein the suction inlet of at least one suction inlet of the gas jet pump (203) is switchedably connected to an outlet of the cathode region (5) by a cathode suction valve (201), or the other suction inlet of at least one suction inlet of the gas jet pump (203) is switchedably connected to an outlet of the anode region (4) by a purge / drain valve (202) through a recirculation line (9) connected to an outlet of the anode region (4). Claim 12 A fuel cell system according to claim 11, wherein the second discharge portion of the multi-directional valve (204) is connected to the discharge air line (14) of the cathode region (5) through the cathode bypass line (208) in which the gas jet pump (203) is positioned. Claim 13 In claim 11, the multi-directional valve (204) is integrated into a component of the fuel cell system (1). Claim 14 A fuel cell system according to claim 13, further comprising, as a component, a gas / gas humidifier (16) disposed upstream of the inlet of the cathode region (5); and a gas / gas humidifier bypass line connected to the inlet air line (13) upstream of the gas / gas humidifier (16) and connected to the exhaust air line (14) of the cathode region (5) upstream of the gas / gas humidifier (16), wherein the multi-way valve (204) is integrated into the gas / gas humidifier (16), or the gas jet pump (203) is disposed in the gas / gas humidifier bypass line in such a manner that the second exhaust of the multi-way valve (204) is connected to the drive inlet of the gas jet pump (203). Claim 15 delete Claim 16 delete Claim 17 delete Claim 18 delete

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